如何识别行中第一次出现特定序列的位置

def find_first_occurrence(sequence, target):
    seq_len = len(sequence)
    target_len = len(target)

    for i in range(seq_len - target_len + 1):
        if sequence[i:i+target_len] == target:
            return i

    return -1  # 如果没有找到匹配的位置，返回-1

# 示例用法
line = "This is a test line. This line contains the target sequence."
target_sequence = "target sequence"

position = find_first_occurrence(line, target_sequence)
if position != -1:
    print("第一次出现特定序列的位置是：", position)
else:
    print("未找到特定序列。")